Field of the Invention
This invention generally relates to a hydraulic brake actuation device. More specifically, the present invention relates to a hydraulic brake actuation device with a support member that guides contact member of a push rod.
Background Information
In recent years, bicycles have been provided with hydraulic braking systems. A hydraulic brake system typically includes a hydraulic brake actuation device, a rotor attached to one of the bicycle wheels and a brake caliper having a slot that receives the rotor therein. The brake caliper has two brake pads that selectively contact the rotor in response to changes in hydraulic pressure in the hydraulic brake actuation device when an actuator such as a lever is moved. Bicycle typically include a front braking system to apply a braking force to the front wheel and a rear braking system to apply a braking force to the rear wheel.
A hydraulic brake actuation device typically has a housing mounted to the bicycle handlebar. The housing includes a master cylinder, a master piston disposed in the master cylinder and an actuation lever pivotally supported on the housing. The housing includes a master cylinder bore with a master piston slidably disposed in the master cylinder bore. By pivoting the actuation lever, the master piston is moved in the master cylinder bore via push rod. Typically, the lever moves the push rod along a linear path. The push rod is often supported by grooves in the housing. The movement of the master piston increases the hydraulic pressure in the brake system such that a slave piston in the caliper is moved. This movement of the slave piston in the caliper causes the brake pads to move together to squeeze the rotor. Some hydraulic brake actuation devices are provided with adjustments for controlling the resting position of the lever to adjust the reach of the lever.
Typically, when the actuation lever of the hydraulic brake actuation device is moved, the slave cylinder(s) also move a corresponding amount. Thus, when the actuation lever of the hydraulic brake actuation device is initially moved, braking contact is delayed because the brake pads must first move and close the gap between the brake pads and the braking surfaces of the rotor. The movement of the brake pads typically corresponds directly movement of the lever arm in a movement ratio. Specifically, for each angular degree of movement of the lever arm, there is a corresponding movement of the brake pads. To control the braking action, some hydraulic braking systems have been provided with an adjustment mechanism for controlling a free stroke of the master piston.